1. Field Of The Invention
The present invention relates generally to the blow-molding of articles from thermoplastic materials, and to resins used in such processes and articles produced by such processes.
2. Description Of The Prior Art
Extrusion blow-molding is a well known technique for production of hollow thermoplastic articles. It involves placing an extruded tube, called a parison, of the thermoplastic in a mold and applying sufficient air pressure to the inside of the tube to cause it to take on the conformation of the mold. Polyethylene is usually used but a number of other materials are adaptable to this method, e.g., cellulosics, nylons, polypropylene, and polycarbonates. It is an economically efficient process and is especially suitable for production of toys, bottles, and other containers as well as air conditioning ducts and various industrial items. The method is not limited to hollow products. For example, housings can be made by blowing a unit and sawing it along the parting line to make two housings.
U.S. Pat. No. 4,261,473 to Yamada et al. discloses a process by which plastic bottles are draw-blow-molded wherein a blend of polymers is used. Among the thermoplastic resins said to be used are polyethylene, polypropylene, polytetrafluoroethylene, polyphenylene oxide and polysulfones.
U.S. Pat. No. 3,711,438 discloses the use of various fillers for thermoplastic resins subjected to various forms of molding including blow-molding.
U.S. Pat. No. 4,652,602 to Liu discloses polycarbonate resins containing mica and/or glass fiber fillers for blow-molding.
The preferred polymer used in the present invention, polyphenylene sulfide, is known, but it has not previously been successfully blow-molded to our knowledge.
Polyphenylene sulfide is commercially available from Phillips Petroleum Company of Bartlesville, Oklahoma, the assignee of the present invention, under the trademark RYTON.RTM.. RYTON.RTM. brand polyphenylene sulfide is marketed in a pelletized form for use in injection-molding and typically has a melt flow, determined in a manner described below, in a range of from about 50 to about 200 g/10 min.